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38 #if defined(HAVE_SCHED_H) && defined(HAVE_SCHED_GETAFFINITY)
41 #include <sys/syscall.h>
48 #include "types/commrec.h"
49 #include "types/hw_info.h"
50 #include "gmx_cpuid.h"
52 #include "gmx_omp_nthreads.h"
54 #include "md_logging.h"
56 #include "gmx_thread_affinity.h"
58 #include "thread_mpi/threads.h"
62 get_thread_affinity_layout(FILE *fplog,
64 const gmx_hw_info_t * hwinfo,
66 int pin_offset, int * pin_stride,
67 const int **locality_order)
69 int nhwthreads, npkg, ncores, nhwthreads_per_core, rc;
72 const int * hwthread_id;
73 gmx_bool bPickPinStride;
77 gmx_fatal(FARGS, "Negative thread pinning offset requested");
81 gmx_fatal(FARGS, "Negative thread pinning stride requested");
84 rc = gmx_cpuid_topology(hwinfo->cpuid_info, &nhwthreads, &npkg, &ncores,
86 &pkg_id, &core_id, &hwthread_id, locality_order);
90 /* topology information not available or invalid, ignore it */
91 nhwthreads = hwinfo->nthreads_hw_avail;
92 *locality_order = NULL;
96 /* We don't know anything about the hardware, don't pin */
97 md_print_warn(cr, fplog,
98 "NOTE: We don't know how many logical cores we have, will not pin threads");
104 if (nthreads > nhwthreads)
106 /* We are oversubscribing, don't pin */
107 md_print_warn(NULL, fplog,
108 "WARNING: Oversubscribing the CPU, will not pin threads");
113 if (pin_offset + nthreads > nhwthreads)
115 /* We are oversubscribing, don't pin */
116 md_print_warn(NULL, fplog,
117 "WARNING: The requested pin offset is too large for the available logical cores,\n"
118 " will not pin threads");
124 /* do we need to choose the pinning stride? */
125 bPickPinStride = (*pin_stride == 0);
129 if (rc == 0 && pin_offset + nthreads*nhwthreads_per_core <= nhwthreads)
131 /* Put one thread on each physical core */
132 *pin_stride = nhwthreads_per_core;
136 /* We don't know if we have SMT, and if we do, we don't know
137 * if hw threads in the same physical core are consecutive.
138 * Without SMT the pinning layout should not matter too much.
139 * so we assume a consecutive layout and maximally spread out"
140 * the threads at equal threads per core.
141 * Note that IBM is the major non-x86 case with cpuid support
142 * and probably threads are already pinned by the queuing system,
143 * so we wouldn't end up here in the first place.
145 *pin_stride = (nhwthreads - pin_offset)/nthreads;
150 /* Check the placement of the thread with the largest index to make sure
151 * that the offset & stride doesn't cause pinning beyond the last hardware thread. */
152 if (pin_offset + (nthreads-1)*(*pin_stride) >= nhwthreads)
154 /* We are oversubscribing, don't pin */
155 md_print_warn(NULL, fplog,
156 "WARNING: The requested pinning stride is too large for the available logical cores,\n"
157 " will not pin threads");
165 fprintf(fplog, "Pinning threads with a%s logical core stride of %d\n",
166 bPickPinStride ? "n auto-selected" : " user-specified",
173 /* Set CPU affinity. Can be important for performance.
174 On some systems (e.g. Cray) CPU Affinity is set by default.
175 But default assigning doesn't work (well) with only some ranks
176 having threads. This causes very low performance.
177 External tools have cumbersome syntax for setting affinity
178 in the case that only some ranks have threads.
179 Thus it is important that GROMACS sets the affinity internally
180 if only PME is using threads.
183 gmx_set_thread_affinity(FILE *fplog,
185 gmx_hw_opt_t *hw_opt,
187 const gmx_hw_info_t *hwinfo,
188 const t_inputrec *inputrec)
190 int nth_affinity_set, thread_id_node, thread_id,
191 nthread_local, nthread_node, nthread_hw_max, nphyscore;
193 /* these are inherently global properties that are shared among all threads
195 static const int *locality_order;
197 static gmx_bool have_locality_order = FALSE;
198 static tMPI_Thread_mutex_t locality_order_mtx =
199 TMPI_THREAD_MUTEX_INITIALIZER;
200 static tMPI_Thread_cond_t locality_order_cond =
201 TMPI_THREAD_COND_INITIALIZER;
203 if (hw_opt->thread_affinity == threadaffOFF)
210 /* If the tMPI thread affinity setting is not supported encourage the user
211 * to report it as it's either a bug or an exotic platform which we might
212 * want to support. */
213 if (tMPI_Thread_setaffinity_support() != TMPI_SETAFFINITY_SUPPORT_YES)
215 md_print_warn(NULL, fplog,
216 "Can not set thread affinities on the current platform. On NUMA systems this\n"
217 "can cause performance degradation. If you think your platform should support\n"
218 "setting affinities, contact the GROMACS developers.");
221 #endif /* __APPLE__ */
223 /* threads on this MPI process or TMPI thread */
224 if (cr->duty & DUTY_PP)
226 nthread_local = gmx_omp_nthreads_get(emntNonbonded);
230 nthread_local = gmx_omp_nthreads_get(emntPME);
233 /* map the current process to cores */
235 nthread_node = nthread_local;
237 if (PAR(cr) || MULTISIM(cr))
239 /* We need to determine a scan of the thread counts in this
244 MPI_Comm_split(MPI_COMM_WORLD, gmx_hostname_num(), cr->rank_intranode,
246 MPI_Scan(&nthread_local, &thread_id_node, 1, MPI_INT, MPI_SUM, comm_intra);
247 /* MPI_Scan is inclusive, but here we need exclusive */
248 thread_id_node -= nthread_local;
249 /* Get the total number of threads on this physical node */
250 MPI_Allreduce(&nthread_local, &nthread_node, 1, MPI_INT, MPI_SUM, comm_intra);
251 MPI_Comm_free(&comm_intra);
255 if (hw_opt->thread_affinity == threadaffAUTO &&
256 nthread_node != hwinfo->nthreads_hw_avail)
258 if (nthread_node > 1 && nthread_node < hwinfo->nthreads_hw_avail)
260 md_print_warn(cr, fplog,
261 "NOTE: The number of threads is not equal to the number of (logical) cores\n"
262 " and the -pin option is set to auto: will not pin thread to cores.\n"
263 " This can lead to significant performance degradation.\n"
264 " Consider using -pin on (and -pinoffset in case you run multiple jobs).\n");
271 if (hw_opt->core_pinning_offset != 0)
273 offset = hw_opt->core_pinning_offset;
274 md_print_info(cr, fplog, "Applying core pinning offset %d\n", offset);
277 /* hw_opt is shared among tMPI threads, so for thread safety we need to do
278 * the layout detection only on master as core_pinning_stride is an in-out
279 * parameter and gets auto-set depending on its initial value.
281 * This is not thread-safe with multi-simulations, but that's anyway not
282 * supported by tMPI. */
288 ret = tMPI_Thread_mutex_lock(&locality_order_mtx);
291 goto locality_order_err;
293 rc = get_thread_affinity_layout(fplog, cr, hwinfo,
295 offset, &hw_opt->core_pinning_stride,
297 have_locality_order = TRUE;
298 ret = tMPI_Thread_cond_broadcast(&locality_order_cond);
301 tMPI_Thread_mutex_unlock(&locality_order_mtx);
302 goto locality_order_err;
304 ret = tMPI_Thread_mutex_unlock(&locality_order_mtx);
307 goto locality_order_err;
313 /* all other threads wait for the locality order data. */
314 ret = tMPI_Thread_mutex_lock(&locality_order_mtx);
317 goto locality_order_err;
320 while (!have_locality_order)
322 ret = tMPI_Thread_cond_wait(&locality_order_cond,
323 &locality_order_mtx);
326 tMPI_Thread_mutex_unlock(&locality_order_mtx);
327 goto locality_order_err;
330 ret = tMPI_Thread_mutex_unlock(&locality_order_mtx);
333 goto locality_order_err;
339 /* Incompatible layout, don't pin, warning was already issued */
343 /* Set the per-thread affinity. In order to be able to check the success
344 * of affinity settings, we will set nth_affinity_set to 1 on threads
345 * where the affinity setting succeded and to 0 where it failed.
346 * Reducing these 0/1 values over the threads will give the total number
347 * of threads on which we succeeded.
349 nth_affinity_set = 0;
350 #pragma omp parallel firstprivate(thread_id_node) num_threads(nthread_local) \
351 reduction(+:nth_affinity_set)
354 gmx_bool setaffinity_ret;
356 thread_id = gmx_omp_get_thread_num();
357 thread_id_node += thread_id;
358 index = offset + thread_id_node*hw_opt->core_pinning_stride;
359 if (locality_order != NULL)
361 core = locality_order[index];
368 setaffinity_ret = tMPI_Thread_setaffinity_single(tMPI_Thread_self(), core);
370 /* store the per-thread success-values of the setaffinity */
371 nth_affinity_set = (setaffinity_ret == 0);
375 fprintf(debug, "On rank %2d, thread %2d, core %2d the affinity setting returned %d\n",
376 cr->nodeid, gmx_omp_get_thread_num(), core, setaffinity_ret);
380 if (nth_affinity_set > nthread_local)
384 sprintf(msg, "Looks like we have set affinity for more threads than "
385 "we have (%d > %d)!\n", nth_affinity_set, nthread_local);
390 /* check & warn if some threads failed to set their affinities */
391 if (nth_affinity_set != nthread_local)
393 char sbuf1[STRLEN], sbuf2[STRLEN];
395 /* sbuf1 contains rank info, while sbuf2 OpenMP thread info */
396 sbuf1[0] = sbuf2[0] = '\0';
397 /* Only add rank info if we have more than one rank. */
401 #ifdef GMX_THREAD_MPI
402 sprintf(sbuf1, "In tMPI thread #%d: ", cr->nodeid);
403 #else /* GMX_LIB_MPI */
404 sprintf(sbuf1, "In MPI process #%d: ", cr->nodeid);
409 if (nthread_local > 1)
411 sprintf(sbuf2, "for %d/%d thread%s ",
412 nthread_local - nth_affinity_set, nthread_local,
413 nthread_local > 1 ? "s" : "");
416 md_print_warn(NULL, fplog,
417 "WARNING: %sAffinity setting %sfailed.\n"
418 " This can cause performance degradation! If you think your setting are\n"
419 " correct, contact the GROMACS developers.",
426 /* any error in affinity setting shouldn't be fatal, but should generate
428 md_print_warn(NULL, fplog,
429 "WARNING: Obtaining affinity information failed due to a basic system error: %s.\n"
430 " This can cause performance degradation! ",
435 /* Check the process affinity mask and if it is found to be non-zero,
436 * will honor it and disable mdrun internal affinity setting.
437 * Note that this will only work on Linux as we use a GNU feature.
440 gmx_check_thread_affinity_set(FILE *fplog, const t_commrec *cr,
441 gmx_hw_opt_t *hw_opt, int ncpus,
442 gmx_bool bAfterOpenmpInit)
444 #ifdef HAVE_SCHED_GETAFFINITY
445 cpu_set_t mask_current;
446 int i, ret, cpu_count, cpu_set;
450 if (hw_opt->thread_affinity == threadaffOFF)
452 /* internal affinity setting is off, don't bother checking process affinity */
456 CPU_ZERO(&mask_current);
457 if ((ret = sched_getaffinity(0, sizeof(cpu_set_t), &mask_current)) != 0)
459 /* failed to query affinity mask, will just return */
462 fprintf(debug, "Failed to query affinity mask (error %d)", ret);
467 /* Before proceeding with the actual check, make sure that the number of
468 * detected CPUs is >= the CPUs in the current set.
469 * We need to check for CPU_COUNT as it was added only in glibc 2.6. */
471 if (ncpus < CPU_COUNT(&mask_current))
475 fprintf(debug, "%d CPUs detected, but %d was returned by CPU_COUNT",
476 ncpus, CPU_COUNT(&mask_current));
480 #endif /* CPU_COUNT */
483 for (i = 0; (i < ncpus && i < CPU_SETSIZE); i++)
485 bAllSet = bAllSet && (CPU_ISSET(i, &mask_current) != 0);
490 if (hw_opt->thread_affinity == threadaffAUTO)
492 if (!bAfterOpenmpInit)
494 md_print_warn(cr, fplog,
495 "Non-default thread affinity set, disabling internal thread affinity");
499 md_print_warn(cr, fplog,
500 "Non-default thread affinity set probably by the OpenMP library,\n"
501 "disabling internal thread affinity");
503 hw_opt->thread_affinity = threadaffOFF;
507 /* Only warn once, at the last check (bAfterOpenmpInit==TRUE) */
508 if (bAfterOpenmpInit)
510 md_print_warn(cr, fplog,
511 "Overriding thread affinity set outside %s\n",
518 fprintf(debug, "Non-default affinity mask found\n");
525 fprintf(debug, "Default affinity mask found\n");
528 #endif /* HAVE_SCHED_GETAFFINITY */